EP 605 801 B1 has already previously made known a detachable plug connection of the type mentioned in the introduction which serves as a hose coupling for the connection of two line portions of a liquid line. The previously known plug connection comprises a sleeve-shaped receiving part, into the sleeve interior of which is insertable a tubular insert part which carries on its outside circumference a retaining projection which is realized as a circumferential annular flange. In the coupling position of the previously known plug coupling, the retaining projection, once the insert part has been pressed into the receiving part, is engaged behind by inwardly directed and elastically sprung retaining edges of a connecting element. The retaining edges of the connecting element, which are produced from hard elastic material, are connected together by means of spring webs, which are combined in a V-shaped manner, and can be elastically sprung as a result of a pressure acting on the combined web end regions of the spring webs in such a manner that the retaining edges are disengaged from the retaining projection. In order to lock the position of the connecting element, plate-shaped press buttons, which in the operating position protrude in each case through a complementarily realized reach-through opening in the circumferential wall of the connecting element, are integrally formed on the combined web end regions. It can be a particular advantage for the connecting element which is connected to the one line portion, the insert part which cooperates with the other line portion and the connecting elements to be able to be realized as plastic material injection molding parts. The production of said plastics material molding parts which are matched to one another, however, is connected to considerable expenditure. Above and beyond this, there is the risk that excessive loads which act on the connecting element and/or the insert part transversely with respect to the longitudinal extension thereof result in a break in at least one of said plastics material parts and in unwanted leakages.
WO 02/079684 A1 has already made known a detachable plug connection, which has a tubular insert part which carries at least one retaining projection on its outside circumference and which comprises a sleeve-shaped receiving part, the interior of which is intended for the insertion of the tubular insert part. The previously known plug connection also has a connecting element which is connected to the receiving part and on which at least one inwardly directly retaining edge is held so as to be able to be bent up or pivoted up, which retaining edge engages behind the retaining projection once the insert part has been pressed in. The previously known plug connection also comprises a locking element which consists of two side walls which encompass the connecting element on both sides as well as a transverse wall which holds them in a U-shaped manner and which (locking element) carries an end plate on the end face. Insert faces, by means of which the locking element is guided on the connecting element so as to be transversely displaceable, are integrally molded on the end edges of the side walls which are remote from the end plate of the locking element. The locking element, which is guided on the connecting element so as to be transversely displaceable, is transversely displaceable between a release position and a locking position. Whereas in the release position a recess, which is provided on the end plate of the locking element, is in alignment in such a manner with the interior of the sleeve-shaped receiving part that the insert part is able to be inserted into the receiving part, in the locking position the locking element engages around the connecting element which is provided on the receiving part in such a manner that a bending up of the connecting element in the region of the retaining edges is prevented.